Conical, because of constant directivity, which is a must for good sound quality both in home and pro environments, but not because of the same reasons.
Square mouth for of the ability to array several of them without radiation pattern interference, which would occur with other shapes like round mouth.
(both is my guess and i am no expert on this)
Square mouth for of the ability to array several of them without radiation pattern interference, which would occur with other shapes like round mouth.
(both is my guess and i am no expert on this)
MaVo said:
The oblate spheroid, if I understand the issues correctly, is really only significantly different from the conical horn in its gradual entry transition. This should minimize internal reflections caused by refraction around steep transitions, leading to HOMs. PB, is that the issue as regards the square shape? If so, it begs the question, can we roughly quantify this to get at how much effect we might see with how much deviation from an OS rate of change? What can we get away with, in other words.
Sheldon
Tom said roughly the following regarding HOM in unities: They are no concern, because the transition of round to square only affects the highest frequencies, since it takes place deep in the horn, where the internal dimensions are acoustically small for most of the audio bandwidth. Same goes for the entry holes. Only waves which WL is much longer than the horn dimension pass them, so no HOM are generated there. Regarding the square shape... i think a OS WG can also be square, as its only difference is in the expansion rate of the first throat centimeters, to smooth the transition between driver opening angle and horn angle.
Thanks. Seems logical. The first few cm of my Unity are essentially round. I'm thinking that it may be worthwhile to lengthen the transition area in the throat to provide a more gradual transition from the driver exit angle to the horn angle. This transition could be OS, at least part of the way. So the remaining question is; how long to make the transition. Or, more to the point, how short can the transition be?
Sheldon
Sheldon
I asked exactly this question in a thread some months ago and tom answered, that he makes it very short, about half an inch or so, because the shorter it is, the higher the detrimental effect will be in the spectrum. He said, that one can choose two options: A) You make the transition as smooth and long as possible in order to suppress negative transitional effects. This way you end up with a OS horn or B) You make the transition as short as possible, to move the negative effects out of the listening bandwidth.
Patrick Bateman said:
Please elaborate as my experiments confirmed to my satisfaction what many other folks at Altec, RCA, etc. long before me concluded that the difference between round, square, and even low aspect ratio radials (< ~1:273) for a given BW/cut-off were so minor as to be moot for all intent and purpose.
GM
MaVo said:
I was more concerned about the transition between driver and horn angle, as that is the more difficult one to do. From round to square is easier to carry out in a gradual manner. Just to be clear, you are referring here to the transition from driver to horn, no?
If the reflections created by a short transition are high in the spectrum, I probably can't hear them anyway, but I wouldn't like my speakers to sound harsh to others who have retained their hf hearing. I don't guess HOM's would readily show up in a typical measurement? Or our hearing might be more sensitive than our measuring method. Here's where simulations might be helpful.
Sheldon
I refer to the transition between round and square. I didnt do a smooth transition between the different angles, because i dont know the driver angle. If you want to have toms exact answer, best thing to do is to look at his post history or make a search for unity horns and read for yourself. I cant explain it better than i have done. I use a transition of 1,5cm and i am happy with it.
MaVo said:
Officially, the lamentably defunct Lambda Acoustics was responsible for offering both kits and finished products, but even using the 'Wayback Machine' yields little useful info, though beyond careful throat, expansion contouring, cosmetics, different HF driver options and possibly 'audiophile' XO component options, they were otherwise the same as the prosound version AFAIK, but you'll need to ask folks who bought them such as WC: http://www.cowanaudio.com/
GM
G'day Mavo
My horn differs little from the one used in the Contractors Cube and other similar products that Servodrive released. The fill in the corners is a little different (cosmetic issue once a different crossover is employed) and the X/O components Nick used are first class, probably better than used by Servodrive. Apart from that, it's the same device. With a small amount of eq (+/- 1 to 2 db) in some points, the horn measures very flat within a huge listening area. I guess this is the ultimate beauty of the Unity Horn in a domestic environment.
Cheers
William Cowan
My horn differs little from the one used in the Contractors Cube and other similar products that Servodrive released. The fill in the corners is a little different (cosmetic issue once a different crossover is employed) and the X/O components Nick used are first class, probably better than used by Servodrive. Apart from that, it's the same device. With a small amount of eq (+/- 1 to 2 db) in some points, the horn measures very flat within a huge listening area. I guess this is the ultimate beauty of the Unity Horn in a domestic environment.
Cheers
William Cowan
GM said:
Mavo nailed it - in a prosound environment, the square mouth is superior because it maximizes the mouth size if your enclosure is cubic.
As for the cut off question, that gets into the ol' waveguide vs horn debate. The mouth size required for a waveguide is dramatically larger than the mouth size required of a horn with equivalent cut off. So in that respect, the researchers from Altec and RCA are looking at a completely different problem than I am. I am concerned with directivity control, not with how low I can play.
MaVo said:
Based on what I've read from Geddes, I do not agree with that statement. As I understand it, the first few millimeters after the diaphragm are the most critical in a horn OR a waveguide. The smallest deviation from "perfect" affects the waveshape all the way down the device. That's why Geddes is so obsessive about the entry angle, the match between the compression driver and the waveguide, and even the phase plug. In fact he owns a patent on interchangeable phase plugs.
Maybe he'll chime in on this thread and elaborate.
ttako said:
Your suggestion *also* gets into the horn vs waveguide debate. The lil' two inch drivers from TB play down to 200hz. If you used a waveguide with a 30" mouth you could maintain directivity control down to 460hz. So why bother putting an eight inch woofer into the waveguide? You're not even running out of low-end with the 2" woofers, right?
Of course Danley is in a different situation; he has clients who are array four of these babies, which gives you a dramatically larger mouth.
Keep in mind that my endeavors are 100% focuse on home and car.
Patrick Bateman said:
If you study the early Bell Labs/WE, RCA, JBL, etc. designs you'll see that the pioneers of audio understood this and my 'adventures' in trying to optimize a pair of Altec 802D loaded 511B horns and later when DIYing horns/WGs finished convincing me beyond all doubt and while I wasn't willing to devote the time/patience to get into phase plug design I have no doubt that different phase plugs are required for different driver/horn/WG combos.
Not all that much new in horn/WG design and those who don't learn from history are doomed to repeat it.
GM
Patrick Bateman said:
Hey John
First, the Unity horn is designed for extremely high SPLs and it is good at that. In the Pro market sound quality is not a major (or certainly not THE major) driving factor (from what I have heard of late its not even a consideration).
So are HOM an issue? No not really, there would be lots of them created by the midranges etc. and those from the throat would not be a big additive issue. But from a sound quality standpoint for lower SPL and smaller rooms, I would contend that the OS waveguides with foam would have a far better sound quality than the Unity. The unity will have lots more SPL. Its a tradeoff.
Someone asked about foam in the unity and yes I believe that the sound quality would be improved, but the SPL loss might be unacceptable as a tradeoff. HOM reduction via foam may not be very effective if serious attention has not been paid to reducing the generation of HOMs in the device itself.
Toms designs are optimized around max SPL, mine around max sound quality. He claims, and I don't doubt it, that his also work well in consumer applications, just as I claim that mine also work well in Pro applications. But make no mistake they are designed and optimized arround different criteria rankings.
GM said:
I would take strong exception to this statement as my letter to the Editor of Audio-X-Press (see www.gedlee.com) will attest to. (This will be published - Ed Dell was quite impressed.) The understanding of waveguides will completely overturn and throw out all prior horn theory based on the Horn Equation. It may take some time, but it will happen. Its alrady started.
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